1. Field of the Invention
The invention relates to an operating device for a gear-changing transmission, example for a gearbox or for an automatic transmission with shift-by-wire operation, according to the preamble of claim 1.
2. Description of Related Art
Gear-changing transmissions for automobiles are generally shifted or controlled with an operating device arranged within the reach of the operator. Typically, operating elements, such as shift levers or selection levers are used which are arranged, for example, between the front seats of the automobile or in other areas of the cockpit.
In particular, it required for ergonomic and safety reasons that presently impermissible shift positions or the execution of the required shifting operations is haptically indicated to the operator in form of corresponding shifting resistances or interlocks on the operating lever. Only in this manner can a haptic shifting operation be realized, like an operation the operator is familiar with or used to, for example, from fully synchronized mechanical gearboxes with their rotation speed and vehicle-speed dependent synchronized interlocks, or from conventional operation of an automatic transmission with its locking mechanism and its gear shift locks.
It is therefore always necessary to transmit to the operator during operation of the transmission an unambiguous tactile feedback about the actual shifting or operating state of the transmission or about the shifting success. However, with electrical or shift-by-wire operation of gear-changing transmissions, there is no longer a mechanical coupling between the operating lever in the passenger compartment and then automobile transmission in the engine compartment. Instead, the shifting commands are transmitted from the operating device to the automobile transmission in the “shift-by-wire” transmission by way of electrical or electronic signals and subsequent predominantly electro-hydraulic conversion of the shifting commands on the transmission. Due to the absence of a mechanical linkage between the transmission actuators and the operating lever, the position of the transmission, any gear shift locks or impermissible shifting commands can no longer provide direct feedback about the position of the operating lever so that it can be sensed by the operator.
For example, with shift-by-wire-controlled transmissions, the driver is unable to easily recognize based on certain shifting positions which are perceptibly blocked on the operating lever that shift lever positions, gear positions and/or shifting commands may not be allowed under the current driving conditions and should therefore also not be selected. Likewise, with a shift-by-wire actuation, the actual execution of the operator's shifting commands by the transmission is also not fed back to the operating lever, so that the operator is unable to receive the haptic sensation when the shifting operation is executed, in the same way he is used to, for example, from mechanically operated gearboxes with their locking mechanism and gear synchronizing locks.
Depending on the position of the gear-changing transmission to be operated and depending other conditions on the automobile—e.g., engine rpm, vehicle speed, clutch position, etc.—, it is therefore necessary for realizing the required haptic feedback with shift-by-wire-controlled transmissions to actively and controllably limit or totally block the movement of the operating lever depending on the state of the transmission.
Only in this way can the operator receive haptic feedback, when he touches the operating lever, with a shift-by-wire-controlled transmission indicating that the intended gear shifting operation—based on the actual vehicle speed or based on a current operating state of the gear-changing transmission—it is not permitted and therefore blocked. In this way, impermissible shifting commands which are recognized by the electronics unit of the transmission and therefore not transmitted from the operating device to the transmission can be prevented from being engaged on the operating lever.
Such actuating mechanism on the operating lever is also required if the operator should be able to receive with a shift-by-wire-controlled transmission the same haptic feedback as with a mechanically operated transmission, such as for example a manual gearbox with a linkage, where engagement of the individual gears on the shift lever generates perceptible counterforces on the operating lever, particularly rpm- and speed-dependent counterforces.
DE 10 2004 041 690 A1 discloses an electric switch, in particular in form of a joystick or cursor switch. The switch has an operating member which cooperates with movement means such that the operating member is adjustable, in particular rotatable, displaceable, pivotable and the like. The movement means is operatively connected with a magneto-rheologically and/or electro-rheologically operating device such that a haptics, in particular a changeable haptics, is produced for the adjustment movement of the operating member. When the operating member is adjusted, the movement means acts on a sensor element to provide a signal and/or for switching.
WO 2005/036031 A1 describes a manual operating mechanism with a lever and an operating element, with each having at least one gear tooth, wherein the gear teeth mesh and can be operated so that they transmit to the operating element a movement of the lever, wherein the meshing gear teeth define a gap occupied by a magneto-rheological fluid, wherein the mechanism further includes one or more magnetic coils which are configured to generate an electromagnetic field in the region of the magneto-rheological fluid and thereby change its viscosity.
To reduce the installation height of a selection lever, in particular of the “shift-by-wire” type, it is known from DE 10 2005 060933 B3 to support the selection lever rod (1) in a housing (10) via a first (2) and a second (3) shaft, which are spatially separated, extend perpendicular to each other and are each displaceable in the axial direction. It then becomes possible to arrange haptic elements stationarily relative to the selection lever rod. Haptic elements may be, for example, also magneto-rheological dampers.
As shown, for example, in DE 198 48 191 A1, attempts have been made in the state of the art to realize a haptics in an operating element for a gear-changing transmission by providing the operating element with an electronically controllable force generating element and/or motion damper which is controlled by a control device, so that the counterforces which accompany the respective state changes in the gear-changing transmission can be simulated on the operating element while the operator operates the operating element.
However, this operating device known from the state-of-the-art with an electronically controllable motion damper has disadvantages because the motion damper according to the teaching of this document must be incorporated as an additional assembly in the region of the operating lever or in the housing of the operating device. This increases the complexity of the structure and requires a separate installation space which is frequently not available with the increasingly smaller operating devices for modern automobile transmissions. In addition, according to the teaching in this document, generation of the restoring force in this document also requires an actuator drive, resulting in not insignificant energy consumption and requiring additional space.
With this background, it is an object of the present invention to provide an operating device with a force-feedback device for haptic simulation—in particular for electric or electronic shift-by-wire operation of a gear-changing transmission—which is able to overcome the aforementioned disadvantages of the state-of-the-art. The operating device should take up little space, have a simple construction and low manufacturing cost. In addition, a reliable and realistic emulation of the haptics of a mechanically locking operating lever should be made possible.